Traditional installation of fire suppression system piping networks uses steel pipe elements with male cut threads joined by female threaded fittings (tees, elbows, reducers) to position sprinklers in specified locations throughout the structure under construction. The cut threaded piping is laborious and messy to prepare and install. Many pipe elements must be prepared on site where they are individually measured and cut to length; their ends threaded using dedicated thread cutting machines, and joined with female threaded fittings using pipe dope and/or tape. Thread cutting is particularly messy, as it involves cutting oil, which contaminates and stains surfaces that it contacts, and oily waste metal cutting chips which must be collected and disposed of.
In view of the disadvantages associated with cut threaded pipe, grooved pipe elements and groove-engaging mechanical pipe couplings and fittings have become the preferred hardware for constructing piping networks. Using grooved pipe elements and groove-engaging mechanical couplings and fittings substantially eliminates the need to cut threads in the pipe elements, as the mechanical couplings and fittings engage circumferential grooves positioned near the ends of the pipe elements. Often the grooves are cold formed in the pipe elements on site using roll grooving machines which do not use cutting oil or produce waste metal chips. Such mechanical pipe couplings also allow fittings which terminate a pipe run to be attached without thread cutting.
However, to complete an installation the sprinkler must be connected to its pipe element. Sprinklers have a male threaded end, and the male threaded end is predominantly smaller (½-¾ inch pipe size) than the 1 inch schedule 40 pipe size that is used, for example, in the so-called “arm-over” configuration described below. In the arm-over configuration, commercially available female-female threaded reducing fittings are used to connect the smaller (male threaded) sprinkler end to the larger (male threaded) pipe element. Thus even when groove-engaging mechanical fittings and couplings are used, this last pipe element that connects to the sprinkler must have male threads cut in the end that joins to the female-female threaded reducing fitting. It would be advantageous to eliminate all thread cutting steps from the process of constructing piping networks for fire suppression systems. It would be further advantageous if it were possible to eliminate the need for a mechanical coupling to seal off a pipe run.